The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to a semiconductor structure including a phase change memory (PCM) cell in which the resistance across the cell changes gradually.
Phase change memory (PCM) is a type of non-volatile random access memory (NVRAM). A NVRAM retains its information when the power is turned off. This is in contrast to dynamic random access memory (DRAM) and static random access memory (SRAM), which both maintain data only for as long as power is applied.
A typically PCM includes a material stack of, and from bottom to top, a bottom electrode, a phase change memory material that exhibits a change in atomic order (from crystalline to amorphous or vice versa), and a top electrode. In such PCMs, the resistance changes abruptly. For some applications such as, for example, analog computing or neuromorphic applications, it is desired to have the resistance of a PCM changing gradually (or at least multiple bits) instead of simply binary resistance states (i.e., high-low resistances).